Thermal Storage Solution for Fertilizer Production

Customer Name – M/s. Deepak Fertilisers and Petrochemicals Corporation Limited

Location – Dahej, Gujarat, India

Completion –

Scope / Requirement –

The client operates a weak nitric acid production plant at Dahej, originally acquired and relocated from a working site in the USA. After recommissioning in India, the plant was unable to achieve the same production capacity as in the USA, particularly during summer months when ambient temperatures were significantly higher. The production process involves compression of ambient air fed to the synthesis process where nitrogen is separated for nitric acid production. The mass of air fed to the synthesis process is the critical parameter for achieving rated output. The client required a solution to cool the compressor suction air without impacting other process parameters, enabling the compressor to push the required mass of air to the synthesis process. Additionally, the 45-meter-tall absorber tower required cooling optimization to improve line productivity.

Challenge –

Thermal Performance Achievement: Cooling ambient air to ISO conditions consistently throughout seasonal variations presented a significant challenge. The solution required appropriate sizing of cooling generation and delivery equipment while selecting the right metallurgy suitable for the ammonia environment present in the plant.

Fluid Dynamic Constraints: Critical limitations existed regarding pressure drop in the intake section of the process air compressor. Any additional pressure drop would adversely affect compressor performance. Equally critical was the risk of suspended moisture particles being carried to the compressor inlet, which could cause massive problems in downstream processes. This demanded precise calculations for selecting appropriate cross-sectional areas and heat exchanger sizing.

Insufficient Steam Availability: The surplus steam available from the recently implemented gas recovery project was insufficient to address peak cooling demand through absorption chillers. The available steam could only meet approximately 70% of the peak cooling demand for suction air cooling, creating a significant capacity gap.

Absorber Tower Cooling Optimization: The 45-meter-tall absorber tower was previously cooled entirely by cooling tower water. Optimizing this cooling system required precision in selecting the right pumping circuit size to handle the substantial height and flow requirements while integrating chilled water for improved productivity.

First-of-its-Kind Implementation in India: With no local reference projects for this type of thermal storage application in industrial settings, the project presented unique design, approval, and execution challenges.

Solution Provided –

Comprehensive Diagnosis and Solution Development: Aqua Chill collaborated closely with the client’s team to diagnose the production capacity issue and arrived at the innovative solution of cooling compressor suction air using absorption chillers, leveraging low-cost steam available from the gas recovery project.

180 TR Vapor Absorption Machine (VAM): Supplied and installed a steam-driven absorption chiller specifically sized for the application, utilizing waste steam from the recovery project as the energy source, making it a highly economical cooling solution.

Innovative Thermal Flywheel System – 111m³ Stratified Thermal Storage Tank: Implemented India’s first industrial thermal storage solution to bridge the gap between available steam capacity and peak cooling demand. The thermal flywheel stores cold energy in the form of chilled water, harnessing substantial variation in hourly cooling load even during peak season. This innovative approach:

• Reduced absorption chiller size by approximately 30%, making it perfectly matched to available steam from the recovery project
• Stored chilled water in distinct temperature layers with cold water remaining under warm water without physical separation, achieved through buoyancy differences at varying temperatures
• Reduced energy consumption of cooling water pumps and cooling tower fans, which otherwise consume fixed power regardless of cooling demand
• Improved chiller COP as substantial cooling generation occurs during nighttime when condenser heat dissipates at lower ambient temperatures

In-House Designed Octagonal Diffuser System: Engineered specialized octagonal diffusers for the thermal storage tank inlet and outlet to maintain stratification integrity. The diffuser design ensures horizontal water distribution across the tank cross-section, preserving distinct temperature layers during charging and discharging cycles without mixing.

Precision-Engineered Suction Air Cooling System: Designed and installed heat exchangers with carefully selected cross-sectional areas to cool ambient air to ISO conditions without adding unacceptable pressure drop. Implemented a unique combination of mist elimination and hydrophobic material filtration to prevent any suspended moisture particles from entering the compressor inlet, protecting downstream processes from potential damage.

Metallurgy Selection: Selected appropriate materials compatible with the ammonia environment present in the fertilizer plant, ensuring long-term durability and safe operation of all cooling system components.

Absorber Tower Cooling Enhancement: Integrated chilled water cooling for a portion of the 45-meter-tall absorber tower cooling load, which was previously handled entirely by cooling tower water. Precisely sized the pumping circuit to handle the substantial height and flow requirements, improving overall line productivity.

Dual Chilled Water Pumping Architecture: Implemented primary and secondary pump systems for optimized operation. Primary pumps charge the thermal storage tank with chilled water from the VAM during off-peak hours when cooling demand is lower. Secondary pumps distribute stored chilled water to the compressor suction air cooling heat exchangers during peak operational hours, ensuring consistent cooling availability.

Comprehensive Instrumentation and Control System: Installed a full-fledged instrumentation and PLC-based Building Management System (BMS) for real-time monitoring and recording of all system parameters including multi-level tank temperatures, flow rates, pressure differentials, and chiller performance metrics.

Best Industrial Practices in Execution: Executed the installation using proven industrial practices in design and execution, coordinating specialized equipment installation, foundation systems, piping integration, and commissioning—all while maintaining ongoing plant operations without disruption.

Project Outcomes

Successfully delivered India’s first-of-its-kind thermal storage solution for industrial fertilizer production, demonstrating innovative engineering to overcome steam capacity limitations while achieving substantial productivity improvements.

Increased Production Capacity: Compressor output increased by 15% or more, enabling the plant to achieve rated production capacity comparable to original USA operations even during Indian summer conditions with higher ambient temperatures.

Optimal Steam Utilization: The thermal flywheel system reduced absorption chiller size by approximately 30%, perfectly matching available steam from the gas recovery project while meeting full peak cooling demand through strategic energy storage.

Energy Efficiency Achievement: Reduced operational costs through lower cooling water pump and cooling tower fan energy consumption. Improved chiller COP by generating substantial cooling during favorable nighttime conditions when condenser performance is enhanced by lower ambient temperatures.

Consistent ISO Conditions: Successfully cooling ambient air to ISO conditions throughout all seasonal variations, ensuring consistent compressor performance and synthesis process efficiency regardless of external temperature fluctuations.

Enhanced Absorber Tower Performance: Partial integration of chilled water cooling in the 45-meter absorber tower improved line productivity while maintaining precise temperature control throughout the tall structure.

Zero Process Impact: Achieved all cooling objectives without adding unacceptable pressure drop or introducing moisture carryover risks to the compressor inlet, protecting downstream synthesis processes and ensuring safe, reliable operations.

Pioneering Installation: Established India’s first industrial thermal storage application for process cooling, setting a benchmark for innovative solutions in fertilizer manufacturing and demonstrating how thermal energy storage can overcome capacity constraints while optimizing existing resources.

This groundbreaking project exemplifies how innovative engineering, practical design, and seamless execution can transform operational challenges into competitive advantages, delivering measurable productivity improvements and energy efficiency in complex industrial environments.

 handling complex, high-spec industrial HVAC environments.